CONFIG_SH_UNKNOWN is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

BareCPU

configname: CONFIG_SH_UNKNOWN

SuperH system type
└─>BareCPU
In linux kernel since version 2.6.12  
"Bare CPU" aka "unknown" means an SH-based system which is not one
of the specific ones mentioned above, which means you need to enter
all sorts of stuff like CONFIG_MEMORY_START because the config
system doesn't already know what it is. You get a machine vector
without any platform-specific code in it, so things like the RTC may
not work.

This option is for the early stages of porting to a new machine.